CVE-2016-4656

The kernel in Apple iOS before 9.3.5 allows attackers to execute arbitrary code in a privileged context or cause a denial of service (memory corruption) via a crafted app.

CVSS: 7.8Highscored by CISA
Exploited in the wild: Yes, in CISA KEV since 24 May 2022CISA deadline for US federal agencies: 14 Jun 2022public exploit code
EPSS: 23.6%chance of exploitation in the next 30 daystop 3% of scored CVEsFIRST score of 11 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 25 Aug 2016analysed here 12 Nov 2026

Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)

Summary

Triage

Attack surface: Server-side
Exploitable: At runtime
Attack vector: local
Weakness: CWE-787 Out-of-Bounds Write
Can a WAF block it?: No. See why

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Products named in our analysis

apple:iphone_os

Fix and mitigation

WAF and other mitigations

Can a WAF block it? No. The attack needs local access to the machine, so a WAF is not on its path.

Also consider: patch

Based on the attack vector (local or physical access). We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Listed since 24 May 2022.
CISA due date: 14 Jun 2022, the remediation deadline for US federal agencies
CISA required action: Apply updates per vendor instructions.
Public exploit code: Yes: 1 on Exploit-DB · 1 Metasploit module
CISA SSVC: exploitation active, automatable no, technical impact totalAssessed by CISA 29 Jan 2025 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Exploit-DB

WebKit - not_number defineProperties UAF (Metasploit)remote, 5 Jun 2018, verified by Exploit-DB

Metasploit

exploit/apple_ios/browser/webkit_tridentexploit, rank manual

Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.

Timeline

25 Aug 2016Published
5 Jun 2018First public exploit or proof of concept648 days (about 2 years) later
24 May 2022Added to CISA KEV (exploited in the wild)1,449 days (about 4 years) later
14 Jun 2022CISA remediation due date (US federal agencies)21 days later
29 Jan 2025CISA SSVC assessment: exploitation active961 days (about 3 years) later
21 Oct 2025CVE record last updated265 days (about 9 months) later
12 Nov 2026Analysed by vulneraibility.com387 days (about 1 year) later

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Metric	Value	What it means
Attack vector	LocalLocal access required (shell, logged-in user).	Local access required (shell, logged-in user).
Attack complexity	LowRepeatable attack, no special conditions.	Repeatable attack, no special conditions.
Privileges required	NoneThe attacker needs no prior access.	The attacker needs no prior access.
User interaction	RequiredA victim must click, open or otherwise cooperate.	A victim must click, open or otherwise cooperate.
Scope	UnchangedImpact stays within the vulnerable component.	Impact stays within the vulnerable component.
Confidentiality	HighTotal data disclosure possible.	Total data disclosure possible.
Integrity	HighComplete modification possible.	Complete modification possible.
Availability	HighFull outage possible.	Full outage possible.

Common questions

Is CVE-2016-4656 being exploited?

Yes. CVE-2016-4656 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.

How severe is CVE-2016-4656?

CVE-2016-4656 is rated High with a CVSS score of 7.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2016-4656?

Yes. A fix has been recorded for CVE-2016-4656. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2016-4656 affect?

CVE-2016-4656 affects apple:iphone_os. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

7 references in the CVE record, grouped by the tags the record gives them.

Advisories (1)

lists.apple.com /archives/security-announce/2016/Aug/msg00000.html

Exploits (1)

exploit-db.com /exploits/44836/

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA KEV catalog: exploitation, date added, due date
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile
Exploit-DB: published exploits
Metasploit Framework: exploit and scanner modules

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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